Field of the Invention
This invention relates to systems for controlling fluid flow in response to electrical pulse control information, such as from a digital computer, microprocessor or the like. Further, this invention relates to improved valves for controlling the rate of fluid flow in such systems.
It is desirable to provide a flow control system wherein flow-rates of control air can be rapidly and accurately varied remotely by automatic control equipment. Such systems previously have often required manually set individual controls for individual settings or, in the alternative, have required position-reading feedback or other additional and/or expensive control equipment. This invention provides both a system and a specific improved valve design meeting these requirements and overcoming prior problems.
Many prior fluid flow control valves proposed for such systems have essentially been pneumatically actuated. Where precise positioning control was necessary, these systems required additional positioning control systems and tended to have slow response time. Various electrically controlled valves using electrical motors required gear trains whereby the ultimate response of the valve was slow as compared to the capability of this invention. A further problem inherent in various prior valves is how to effectively counteract the increase in pressure exerted against the valve as it is driven closer to a fully closed position due to the pressure maintained by the fluid in the system. One solution has been to employ a motor with a drive capacity much larger than needed to counteract this force. However, this results not only in an inefficient use of the motor but also an expensive solution to the problem by using a motor much larger than necessary to operate the valve. In summary, prior art devices have presented numerous shortcomings in applications requiring specific rapid and precise positioning responses particularly where a low-cost valve is required.
This invention provides a simple control including a linearly movable variable orifice valve which is remotely adjusted by electrical control pulses which operate an electric stepping motor to provide direct, precise and exact movement of an internal valve spool. No positional feedback is required. The invention is capable of providing as little as 0.001 inches of linear translation with each control power pulse to the motor depending upon the specific motor selected for use with the valve. By providing the internal spool and orifice with the appropriate dimensions such a valve can produce a linear rate of change in the fluid flow or logarithmic rate change or any other desirable rate adjustment within much more precise and definite limits as compared with prior devices. Accordingly, this device allows for quick response time and accurate fluid flow rate changes in a simple and inexpensive control unit.